How long does it take the water to heat up in a gas water heater that has been drained and refilled as part of the yearly maintenance?

It should not take any longer than it always used to take, to heat the water after you have left it turned off for say a week - like if you went away from home for a holiday. If it does not heat the water you could check two things yourself: * is the Gas supply actually turned "On"? (It may have been left turned "Off".)

* has the water temperature thermostat been turned to a very low temperature or even to "Off"? If the Gas supply is definitely "On" and the thermostat setting is set to a normal temperature then something else inside the unit may not have been reset from "Off" to "On" by the technician who did the yearly maintenance.

The best advice anyone should give you is to call that maintenance technician back to fix the problem!